Marking and detection of subsurface defects in multi-layer hose structures

ABSTRACT

Subsurface defects in multi-layer hose structures are marked as to location and extent with a tape having an axial stripe of radioactive salts thereon which is subsequently detected with scintillation counters that are connected to circuits and controls which mark or remove the faulty section of the hose structure after completion of the hose. The radioactivity of the salt is capable of being detected through the subsequent layers of the hose structure which cover the tape as the manufacture of the hose continues after the defect is coded with the tape.

United States Patent Groezinger [151 3,678,271 1 51 July 18,1972

[54] MARKING AND DETECTION OF SUBSURFACE DEFECTS IN MULTI- LAYER HOSESTRUCTURES [72] Inventor: John J. Groezinger, Peoria, Ill.

[73] Assignee: Caterpillar hector Co., Peoria, lll.

[22] Filed: Oct. 9, 1969 [21] Appl. No.: 865,020

52 us. or. ..250/71.5 11, 250/106 T 511 161. C1. .001: 1/20 [58] FieldofSearch ..250/106T, 106 sc, 83.3IR, 250/836 Fl, 71.5

[56] Refmllm Cited I UNITED STATES PATENTS 2,856,539 10/ 1958 Onhuber etal ..250/83.3 H

PULSE HEIGHT ANAYLZER RATEMETER AND COMPARATOR Payne et al. ..250/l06 SCX Moses ct al.... ....250/l06 SC X Gith ..250/ 106 T X PrimaryExaminer-Archie R. Borchelt Attorney-Fryer, Tjensvold, Feix, Phillips &Lernpio ABSTRACT Subsurface defects in multi-layer hose structures aremarked as to location and extent with a tape having an axial stripe ofradioactive salts thereon which is subsequently detected withscintillation counters that are connected to circuits and controls whichmark or remove the faulty section of the hose structure after completionof the hose. The radioactivity of the salt is capable of being detectedthrough the subsequent layers of the hose structure which cover the tapeas the manufacture of the hose continues after the defect is coded withthe tape.

7Clains,4Drawingflgures RELAY CONTROL CIRCUIT HOSE MOVEMENT SPRAY RINGPATENTED JUL 1 8 m2 SHEET 1 OF 2 INVENTOR JOHN J. GROEZINGER .0 1 g 9?ZITORNEYS PATENTED JUL 1 8 I972 v sum 2 BF 2 INVENTOR JOHN J. GROEZINGERwwv -w ATTORNEYS BY W, W

MARKING AND DETECTION OF SUBSURFACE DEFECTS IN MULTI-LAYER HOSESTRUCTURES BACKGROUND OF THE INVENTION In the manufacture ofhigh-pressure hydraulic hose multiple and concentric layers of rubber,fabric and reinforcing are wrapped on a mandrel to build up the hosestructure in stages. Usually the hose construction consists of the coreof elastomer and fabric on which wire reinforcing is would in a helicalor spiral manner, usually wound in an opposite direction in adjacentplies, which are normally separated by insulating layers of elastomer.Once the hose structure has been completed an outer elastomer casing orcover is applied and the hose is subsequently cured under heat pressure.Conventionally, shrink tape is wrapped around the outer casing for thecuring step. Thereafter the mandrel is removed from the center of thehose and the hose is further processed into the hydraulic assemblies ordesignated lengths of hose. The manufacture of high-pressure hydraulichose, such as referred to above, is disclosed and illustrated in theassignees U. S. Pat. No. 3,357,456 issued to Grawey et al. and referenceis made thereto for a more detailed description of the hosemanufacturing process.

During the manufacture of the hose and the application of any of theseveral concentric layers or plies, a defect may occur in themanufacturing process which will be covered by the subsequent plies asthey are applied. conventionally, when such a defect occurs, theoperator will measure the extent of the defect and also measures thedistance of the defect from an end of the supporting mandrel. Themandrels, which can be up to 50 feet in length, are tagged and themandrel tag, the defect in inches and its distance from the end of themandrel are all entered into a log so that the defective section of thehose can be subsequently located and removed after the hose has beencompleted. It can be appreciated that upon completion of the hose itwill be necessary to measure the hose to determine the location and theextent of the defect since no sign of the defect is visible on thesurface of hose.

Using such a cumbersome log system, a number of errors are likely tooccur. Obviously, there are errors in the measurement of the location ofthe defect from the end of the mandrel, inaccurate recording of thesemeasurements, figure transpositions, etc., which often result inremoving the good sections of the hose and allowing defective sectionsto pass on to further processing where the defects may or may not befound. This increases expense and decreases quality control. Of course,the additional man hours required to physically measure the length ofhose at least twice along with the record keeping is likewiseundesirable and costly.

The above log-record method has been conventionally employed in themanufacture of hydraulic hose since other techniques which destroy theconcentricity of the hose structure are unsuitable for a variety ofreasons. For example, any marker that destroys the concentricity of thehose can cause difficulty when additional layers or plies are added tothe hose carcass during subsequent manufacturing operations. As aresult, the log-record technique in the past has been the only suitableway to keep track of the subsurface defects which are covered bysubsequent layers of the hose structure. Since the hose is made onmandrels, it is impossible to cut out defective portions of the hose asthey occur since the manufacturing process is a continuous unit processas described in the aforementioned patent.

Thus, it is an object of the instant invention to provide an improvedtechnique for marking and detection of subsurface defects in hydraulichose both as to location and extent without changing its concentricity.

A further object of the invention is to provide a simple technique formarking and subsequent detection of subsurface defects which requiresfewer man hours and that will substantially eliminate the human errorfactor in such operations.

A further object is the provision of an apparatus whereby detection andmarking or removal of defective hose sections can be accomplishedautomatically.

A collateral object of the invention is the provision of a specialadhesive tape consisting of two layers having a center stripe ofradioactive salt sandwiched between the tape layers which can beemployed to mark subsurface defects in hydraulic hose.

It is also an object of the current invention to provide suitableapparatus for detection and marking hose having subsurface defects,coded with the tape.

It is also an object of the invention to provide a double layeredadhesive tape having a stripe of radioactive salts down its center linewhich is safe for manual handling so that operators of hose plants canemploy it to mark subsurface defects during the manufacture of hose.

Other objects and advantages will be apparent from the description whichfollows.

SUMMARY OF THE INVENTION A radioactive marking and tracing tape formarking subsurface defects in hose structures and the like includes astripe of radioactive salts disposed along the center line of one layerof an adhesive faced tape and on a surface which is covered by a secondlayer of said tape encapsulating said stripe of radioactive salts in asandwich tape laminate having at least one exposed adhesive face. Thismarking and tracing tape is attached to defective areas in hosestructures and the like through its exposed adhesive face to mark thelocation and extent of subsurface defects (the length of tape beingequal to the length of the defect) which are subsequently covered byadditional layers of the fabricated structure. Detection of the tape anda marking of the outer surface of the finished structure is accomplishedwith scintillation detectors connected to circuits and controls to markor remove portions of the finished structure corresponding to thatmarked with the length of said tape laminate. The scintillationdetectors are connected to a pulse analyzer, comparator, time delaycircuits and a marker or cutter to form the apparatus for automaticallymarking or removing defective sections of the fabricated structure.

BRIEF DESCRIPTION OF THE DRAWINGS The current invention will be betterunderstood by reference to the attached drawings in conjunction with thedescription herein.

FIG. 1 is an elevation of the machine for the manufacture of thelaminated radioactive marking and tracing tape;

FIG. 2 shows an elevation with parts of the cover broken away exposing asubsurface defect in an inner layer or ply of reinforced hose taggedwith the laminated radioactive marking and tracinG tape;

FIG. 3 illustrates a detection and marking system for employment inconjunction with the radioactive tape to band the outer surfacehydraulic hose structures over subsurface defects along with a manualcut-off saw for removing the banded portions of the hose; and

FIG. 4 is a schematic illustration of the circuitry for the systemillustrated in FIG. 3.

BRIEF DESCRIPTION OF A PREFERRED EMBODIMENT In the practice of theinvention, it is necessary to prepare the laminated radioactive markingand tracing tape which is accomplished with a laminate forming machine10, illustrated in FIG. 1. The machine includes a base 11 which supportsa vertical plate 12 on which two tape bobbins l3 and 14 are mountedalong with an idler roller and a power take-up reel 16 whose drive motorand reduction gearing 17 are illustrated by broken lines Each tapebobbin and the idler roller includes a roller bearing 18 mounted on aboss 19 which is secured to the face of the plate with a bolt 20.

Mounted on tape bobbin I3 is a roll 21 of adhesively faced tape whosefree end 22 is threaded over the idler roller 15 to the take-up reel 16,as illustrated in FIG. 1. Similarly, another roll 23 of adhesively facedtape is mounted on bobbin 14 with its free end 24 threaded across theidler roller so that it is in registry with the free end of roll 21whereby the adhesive face 22a of this latter roll will join the twotapes in a laminated twoply tape 25 which is wound on the take-up reel.An adhesive face 240 of roll 23 will provide an adhesive surface bywhich the laminated tape can be attached to partially fabricatedstructures for marking and tracing defects which are subsequentlycovered by additional layers of the structure.

Mounted adjacent to roll 14 is a stylus 26 which is pivoted about pin 27so its writing point 28 will track on the peripheral surface of thisroll, as illustrated in FIG. 1. A biasing spring 29 is connected to theopposite end of the stylus and it urges the writing point intoengagement with the roll surface insuring positive writing contact.

The stylus may consist of a fountain pen or similar writing device whichhas its writing point contacting the center line of the tape to write orprint a stripe on the center line of roll 23 as it unwinds from itsbobbin 14. The reservoir of the stylus is filled with an ink-likesubstance which includes a soluble salt of a radioactive salt having ashort half life. For example, salts containing iodine-131, gold-198, orchromium-51 are suitable. A suitable concentration of the radioactivesalt along the center line of the tape for marking and tracing defectsin hydraulic hose should yield approximately 0.85 microcuries per inchbut the linear specific activity can be adjusted, as a situationdemands. All of the above salts have short half lives and this isdesirable in order to reduce the problems involved in the disposal ofthe scrapped hose which has been marked with the tape and removed.

When the take-up reel 16 is winding the laminated marking and tracingtape, the stylus tape writes or prints a stripe in the center of thetape as it egresses from its roll 23 and this strip is monitored by aGeiger Mullar tube 30 as it progresses to the idler roller which isconnected to recording ratemeter 31 for making the appropriate reportsto the AEC. Commercially available SCOTCH tape can be employed andeither the single faced adhesive or double faced adhesive type issuitable. it may be desirable to use the double faced adhesive tape forroll 23 to insure the better bonded laminate tape.

It should be appreciated that the two layers of tape are broughttogether so the stripe of radioactive salts printed or written along thecenter line of the tape leaving roll 23 is sandwiched between the twolayers. This encapsulaton reduces a likelihood that any of theradioactive salts will be inadvertently dispersed after the ink dries orduring use of the resulting laminated tape. Further, it allows thelaminated radioactive tape to be placed on a convention office tapedispenser and placed in the hose plant without danger to personnel,since ingestion or contact with the radioactive salt is almost precludedby the laminated sandwich arrangement.

In FIG. 2 a portion of hydraulic hose 40 is illustrated with partsbroken away to show the employment of the radioactive marking andtracing tape. A series of broken wires 41 are illustrated in the hosestructure and are marked with a piece of the laminated tape 42 having aradioactive stripe along the center line which tape is normally coveredby the outer cover or casing 43 of the hose structure. It is to be notedthat the length of tape is applied along the full length of the defectso that the axial stripe on the tape is coextensive with the defect. Asa result the marking and tracing tape can accurately pinpoint both sidesof the defect so that it may be ultimately removed without wastingadditional portions of the hose structure.

After the defect has been marked with the tape, manufacture of thehydraulic hose is continued until the total manufacturing process hasbeen completed and the mandrel has been removed from the hose core. Atthis point the hose is routed through a detection and marking unit 50illustrated in FIG. 3. This unit consists of a thick circular leadshield 51 with the central aperture 52 wherein through which thecompleted hose structure is passed. Four bores extend from the surfaceof the lead shield to communicate with the aperture through which thehose passes. These bores are indicated by broken lines 53 and arelocated at right angles to one another. Mounted in each bore withappropriate shielding are sodium iodide scintillation detectors whichwill monitor the hose as it passes through the aperture. These detectorswill, through the circuitry illustrated schematically in FIG. 4, operatea paint spray ring 54 mounted adjacent to the shield to spray a band Aon the hYdraulic hose passing through the aperture which correspondsexactly to the subsurface position of tape strip 42. Subsequently, thehand-operated saw 55 can be employed to cut out the defective bandedsection of the hose.

Referring to FIG. 4 the sodium iodide scintillation detectors 60 areshown arranged about the hose structures without the circular leadshield and other shielding normally employed to lower backgroundradioactive radiation. Each detector is connected to a pulse heightanalyzer 61. The pulse height analyzer discriminates to increase thesignal-to-noise ratio and accepts radiation energy levels having theknown energy of the radioactive salt employed in the stripe. Theanalyzer forwards resulting signals to a ratemeter and comparator 62.The ratemeter and comparator will provide an output signal directlyrelated to the position of the tape relative to the four circularlyarrayed detectors as the hose passes through their detection circle. Inthe ratemeter and comparator the count rate is averaged over a presettime constant and changes in the count rate caused by the presence ofthe tape strip 42 and the detection circle or field of the detectors 60will cause the ratemeter and comparator to supply signal to the timedelay circuits 63 whose output is connected to relay 64 that operates asolenoid 65. This solenoid is connected to control the air flow to aspray ring 54 which sprays a band of paint about the circumference ofthe hose as it passes through the spray ring. The band correspondsexactly to the position of the underlying laminated tape in thesubsurface portions of the hydraulic hose structure.

Using the above parameters the hydraulic hose can be moved through thedetection circle of the circular array of scintillation detectors 60 ata rate of approximately 38 feet per minute and the time delay circuitsare adjusted to compensate for the distance between the detection circleand the spray ring and the relative movement of the hose through thedetection and marking system 50.

The above circuit components are fairly conventional and can be obtainedfrom various sources for forming the combined circuit described above.

I claim: 1. A self-sticking marking and tracing tape for markingsubsurface defects in multi-layer hose structures and the likecomprising two layers of adhesive faced tape assembled in registry toform a laminate through utilization of one of said adhesive faces, oneof said tape layers having a continuous stripe of radioactive salts ofuniform radioactivity along its length disposed on its surface which iscontiguous to the other tape layer in said laminate, said stripecentrally disposed wherein said stripe of said radioactive salts isencapsulated between said two layers, said laminate having at least oneadhesive face.

2. The marking and tracing tape as defined in claim 1 wherein the halflife of the radioactive salts in the stripe is less than 60 days.

3. A method of tagging subsurface defects as to location and extent inmulti-layer hose structures and the like which are covered over bysubsequent layers of the structure comprismg:

placing a strip of a self sticking two layer laminated tape having acontinuous stripe of radioactive salts of uniform radioactivity alongits length disposed on its center line along said defect at the time itoccurs, said strip having a length substantially coextensive with thelength of said defect; subsequently detecting the location of said tapeby its radioactive emissions coming through overlying layers of thestructure when the structure has been completed; and

indexing the outer surface of said structure to correspond withunderlying position of said strip of tape by detection of the beginningand end positions of said stripe of radioactive salt.

7. The method defined in claim 3 wherein the detection of the underlyingposition of the strip of tape is accomplished by passinG the finishedstructure through a circular array of scintillation detectors, recordingthe beginning and end points of the underlying stripe of radioactivesalts on said strip and subsequently indexing the exterior surface ofthe structure as it moves beyond said detectors by use of said recordingof said points to control the indexing means.

l 1' i i t

1. A self-sticking marking and tracing tape for marking subsurfacedefects in multi-layer hose structures and the like comprising twolayers of adhesive faced tape assembled in registry to form a laminatethrough utilization of one of said adhesive faces, one of said tapelayers having a continuous stripe of radioactive salts of uniformradioactivity along its length disposed on its surface which iscontiguous to the other tape layer in said laminate, said stripecentrally disposed wherein said stripe of said radioactive salts isencapsulated between said two layers, said laminate having at least oneadhesive face.
 2. The marking and tracing tape as defined in claim 1wherein the half life of the radioactive salts in the stripe is lessthan 60 days.
 3. A method of tagging subsurface defects as to locationand extent in multi-layer hose structures and the like which are coveredover by subsequent layers of the structure comprising: placing a stripof a self sticking two layer laminated tape having a continuous stripeof radioactive salts of uniform radioactivity along its length disposedon its center line along said defect at the time it occurs, said striphaving a length substantially coextensive with the length of saiddefect; subsequently detecting the location of said tape by itsradioactive emissions coming through overlying layers of the structurewhen the structure has been completed; and indexing the outer surface ofsaid structure to correspond with underlying position of said strip oftape by detection of the beginning and end positions of said stripe ofradioactive salt.
 4. The method defined in claim 3 wherein the indexingis accomplished by applying a visual mark co-extensive with the stripeto the outer surface of the structure.
 5. The method defined in claim 4wherein the visual mark is paint sprayed on the exterior surface of thestructure.
 6. The method defined in claim 3 wherein the indexing isaccomplished by removing the portion of the structure containing thestrip of tape by cutting through the structure at both ends of thecontinuous stripe of radioactive salts.
 7. The method defined in claim 3wherein the detection of the underlying position of the strip of tape isaccomplished by passinG the finished structure through a circular arrayof scintillation detectors, recording the beginning and end points ofthe underlying stripe of radioactive salts on said strip andsubsequently indexing the exterior surface of the structure as it movesbeyond said detectors by use of said recording of said points to controlthe indexing means.